Template:Infobox helium

Helium, ₂He

Helium
Pronunciation	/ˈhiːliəm/ ​(HEE-lee-əm)
Appearance	colorless gas, exhibitin a reid-orange glow when placed in a heich-voltage electric field
Standard atomic weight Ar, std(He)	7000400260200000000♠4.002602(2)
Helium in the periodic cairt
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Airn Cobalt Nickel Capper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Siller (element) Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gowd Mercur (element) Thallium Leid (element) Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Ununtrium Flerovium Ununpentium Livermorium Ununseptium Ununoctium - ↑ He ↓ Ne hydrogen ← helium → lithium
Atomic nummer (Z)	2
Group	group 18 (noble gases)
Period	period 1
Block	s-block
Element category	Noble gas
Electron confeeguration	1s2
Electrons per shell	2
Pheesical properties
Phase at STP	gas
Meltin pynt	(at 2.5 MPa) 0.95 K ​(−272.20 °C, ​−457.96 °F)
Bylin pynt	4.22 K ​(−268.93 °C, ​−452.07 °F)
Density (at STP)	0.1786 g/L
when liquid (at m.p.)	0.145 g/cm3
whan liquid (at b.p.)	0.125 g/cm3
Creetical pynt	5.19 K, 0.227 MPa
Heat o fusion	0.0138 kJ/mol
Heat o vapourisation	0.0829 kJ/mol
Molar heat capacity	5R/2 = 20.786 J/(mol·K)
Vapour pressur (defined bi ITS-90) P (Pa) 1 10 100 1 k 10 k 100 k at T (K)     1.23 1.67 2.48 4.21
Atomic properties
Oxidation states	0
Electronegativity	Pauling scale: no data
Covalent radius	28 pm
Van der Waals radius	140 pm
Colour lines in a spectral range Spectral lines o helium
Ither properties
Naitural occurrence	primordial
Creestal structur	​hexagonal close-packed (hcp)
Speed o soond	972 m/s
Thermal conductivity	0.1513 W/(m·K)
Magnetic orderin	diamagnetic
CAS Nummer	7440-59-7
History
Diskivery	Pierre Janssen, Norman Lockyer (1868)
First isolation	William Ramsay, Per Teodor Cleve, Abraham Langlet (1895)
Main isotopes o helium
Iso­tope Abun­dance Hauf-life (t1/2) Decay mode Pro­duct 3He 0.000137%* stable 4He 99.999863%* stable
Atmospheric value, abundance mey differ elsewhaur.

style="text-align:left"| data m.p. cat
	in	calc from C	diff	report	ref
C	−272.20	—	—
K	2.5	0.950	1.55
F	−457.96	−457.960	0
WD	-272.05 !-272.05 Celsius
input	C: −272.20, K: (at 2.5 MPa) 0.95, F: −457.96
comment

style="text-align:left"| data b.p. cat
	in	calc from C	diff	report	ref
C	−268.93	—	—
K	4.22	4.22	0
F	−452.07	−452.07	0
WD	-268.9 !-268.9 Celsius
input	C: −268.93, K: 4.22, F: −452.07
comment

References

Thir references will appear in the airticle, but this list appears anerly on this page.